Engine starter



July 20, 1948. K. F. DOUGLAS 2,445,609

ENGINE STARTER Filed March 29, 1946 ill! INVENTOR.

WITNESS-'7 I ay w ATTORNEY Patented July 20, 1948 Kenneth Douglas,Elmira,

N. Y., assignor to Bendix Aviation Corporation, a corporation ofDelaware,

Application March 29, 1946, Serial No. 558,019

4 Claims.

The present invention relates to engine starters and more particularlyto-means for defining the idle position of a starter drive pinion andinsuring traversal thereof upon energization of the starting motor.

It is an object of the present invention to provide a novel starterdrive embodying unitary means for defining the idle position of thedrive pinion, for assuring traversal of the pinion when the starting isenergized, and for preventing rebounding of the pinion when it is thrownback to idle position by the self-operation of the engine.

It is another object to provide such a device incorporating a re-entryspring for assuringtraversal of the starter pinion out of idle positionand novel retaining thimbles for said spring.

It is another object to provide such a device in which the retainingthimbles for the re-entry spring can be used interchangeably at eitherend of the spring, the thimble at the rear of the spring being held inplace by interlocking means in. the nature of a bayonet joint.

It is another object to provide such a device which is economical tomanufacture and which may be easily and quickly assembled anddisassembled.

Further objects and advantages will be apparent to those skilled in theart from the following description taken in connection with the accompanying drawing, in which I Fig. 1' is a side elevation partly insection of a preferred embodiment of the invention showing the parts inidle position;

Fig. 2 is a section taken substantially on the line 22 of Fig. 1illustrating the locking mechanism for the thimble;

Fig. 3 is a detail in perspective of one form of retaining thimble forthe re-entry spring;

Fig. 4 is a detail in side elevation of the retaining thimbleillustrated in Fig. 3, partly broken away to show one of the anchoringstuds therefor; and

Fig. 5 is a detail in elevation of a modified form of retaining thimble.

In Fig. 1 of the drawing, there is illustrated a power shaft l which maybe the armature shaft of a starting motor not shown. Shaft I has areduced extension 2 providing an abutment shoulder 3 against which athrust ring 4 is preferably seated. An actuating member in the form of ahollow shaft 5 is fixed to the outer end of the power shaft I by anysuitable means such as a cross pin 6. Shaft 5 is threaded for a portionof its length as shown at l, and has a smooth reduced intermediateportion 8. An engine driving member in the form of a pinion 9 isslidably journalled on the power shaft between the shoulder 3 and screwshaft 5 for traversal into and out of mesh with an engine gear I I.

Means for actuating the pinion 9 from the screw shaft 5 is providedcomprising a control nut I2 on the screw shaft and a yielding drivingconnection including a block I 3 of elastically deformable material suchas rubber seated on the control nut l2 against a radial flange l4 formedthereon, and bearing at its forward end against the radial flange [5 ofa thimble I 6 which is suitably attached as by welding to a flangemember l! rigidly mounted on the pinion 9 as indicated at l8. The rubberblock I3 is preferably held under initial compression by meansof abarrel member I9 surrounding the rubber block, having an internalshoulder 2| at its rear end engaging the flange 14 of control nut l2,and being provided with an annular internal recess 22 at its forward endin which the peripheries of the flanges I5, I! are received and retainedin any suitable manner as by spinning over the end of the barrel asshown at 23.

The control nut I2 is counterbored in its forward end as shown at 24 sothat when the pinion is in idle position as illustrated, it has runoffthe ends of the threads 7 on the screw shaft and bears rotatably on thesmooth portion 8 thereof. Means for yieldably retaining the control nutin idle position is provided comprising a pin 25 mounted in the controlnut with freedom for radial movement, and a spring ring 26 pressing thepin into frictional contact with the screw shaft 5, the latter beingpreferably provided with a shoulder 27 so positioned as to be engaged bythe pin immediately after the threads of the nut have entered the threadspaces of the screw shaft.

According to the present invention, unitary means are provided forapplying yielding pressure to the control nut l2 to assure entry of thethreads thereof into the thread spaces of the screw shaft, which meansalso serves to arrest the backward movement of the control nut with itsassociated parts when the pinion is thrown out of mesh as the enginestarts, and to apply a frictional retarding effect to said parts whilethey are overrunning the screw shaft. As here shown, this meanscomprises a thimble 28 slidably mounted on the rear end of the screwshaft, having a radial flange 29 adapted to be engaged by the adjacentend of the control nut 12, longitudinal movement of the thimble to theright in Fig. 1 being limited by a shoulder 3| on the screw shaftengaging the inturned end 32 of the thimble. A similar thimble 33 isalso mounted on the end of the screw shaft reversely to the thimble 28,and a compression spring 34 is mounted on said thimbles between theflange 29 of thimble Z8 and a similar flange 35 on thimble 33.

The thimble 33 is retained on the end of-the screw shaft 5 by a quicklydetachable connection in the nature of a bayonet joint. For this purepose, a plurality of studs 36 are seated in the end of the screw shaft,projecting therefrom sufli, ciently to bear loosely within the thimble 33, and the latter has an inturned flange 31 provided, with slots 38arranged to permit the thimble to he slid over said studs, and withdepressions 39 intermediate said slots adapted to form seats forreceiving said studs when the thimble is'iOtated to bring the seats intoregistry therewith. The in u ne f n 32 of th e 28 s simila y formedwithslots and depressionsinorder to permit assembly of the thimble over thestuds 36, and to makev the thimbles completely interchangeable,

In assembling this drive, the control nut with it ass c at d parts. isfirst mo nt on h scre shaft, the screw shaft is placed on the powershaft land anchored thereto by the pin 5., the. thimble 2,8. is thenslid on the end of the screw shaft, spring 3.4.placed thereon andthimble 33 pressed over the studs 36 and rotated until the latter seatin the. depressions 39. The thimble 33' then serves t 'l kthe pin, 6 andthe stud 3 in p s tion, and the, pressure of the spring against, thestuds so as to prevent, rotation of the thimble on the screw shaft.

The dimensions of the. parts are such that the spring 34 presses thecontrol nut 12 into initial engagement with the threads of the screwshaft 5,, further expansion of the spring being limited by engagement ofthe flange 32 of thimble 28 with shoulder 3! n the screw shaft, whichengagement occursat about the same time that the anti-drift pin 25 inthecontrol nut engages the shoulder 21 of the screw shaft.

In peration, sta ting with the parts in the positions. shown in Fig. 1,rotation of the power shaft 1' causes the control nut 12 to be traversedto th right, causin the pinion 9 to m th the. engine. gear I l, and whenl n tud nal move ment of the pin on is ar t by n a me with the thrustcollar 4, the rubberb lock 13 is compressed and torqued to yieldablytransmit the power of the starting motor to the engine gear. When the,engine starts, the acceleration of the pinion 9 is transmitted to thecontrol, nut l2, which is accordingly thrown back to idle position,running off the ends of the threads I of the screw shaft. The impact ofthe control nut, and the parts associated therewith is cushioned by thespring-pressed thimble 28, and the energy of rotation ofjhe parts isdissipated by the frictional engagement of the nut and thimble so as toeliminate any tendency of the parts to rebound, Thereafter, the partsare retained in idle posit n y m an of he ant ri t P n 34 holds thethimble Although but one embodiment of the invention has been shown anddescribed in detail, it will be understood that other embodiments andadaptations are possible without departing from the spirit of theinvention as defined in the claims appended hereto.

h t 5-. la med is:

1, In an engine starter, a power.- shaft, a hollow shaft threaded for a,portion of its length fixed on the power shaft, a pinion slidablyjournalled on the power shaft for movement into and outcf mesh with agear of an engine to be started, means for actuating the pinion from thescrew shaft-including a control nut threaded on the screw shaftand-arranged to run off the threaded portion thereof when the pinion isdemeshed fromrthe engine gear, and means for urging the control nut intoinitial engagement with the threads of the screw shaft including athimble having a limited sliding engagement with thescrewfshaitandadapted' to engage the control nut, a co'rnpression springsupported at one end cj'said-thimble, a second thimble mounted on thescrew'shaft'supporting-the otherend of the spring, and means providing abayonet connection between the secondthimble and the screw shaftepositionedas -tomaintain the spring under initial compression.

2: An engine starteras set forth in claim 1 in which said bayonetconnection comprises a plurality of studs mounted in the screw shaft,said second thimble. having an equal number of slots adapted to registerwith the studs during assembly ef the parts, to permit" passage of thethimble over the studs, saiclthiinblealso having an equal numberofdepressions intermediate the slots adapted to receive the studsand-lock the parts together. V M

'3. engine starter asse-tfiorthin' claim 1 in which said bayoneteonnection comprises a plurality of studs mountedlinth e screwshaft,said second thimble being formed to surround the studs and hold them inthe screw shaft. I

'4.- In an engine starter apower shaft, a hollow screw shaft mountedthereon, a pin anchoring the screw shaft on-the power shait, a pinionslidably mounted on the power shaft, actuating means-for the pinionincludinga control nut having a threaded connection vv-iththe screwshaft, and yielding means for initiating longitudinal movement of thecontrol nut on the screw shaft comprising a spring and a thimble forminga seat therefor, studs in the screw shaft for locking the thimblethereon, said thimble being arranged to surround and prevent-radialmovement of said cross pin and studs.

F-. DOUGLAS.

REFERENCES: CITED UNITED STATES PATENTS Name Date wi tarc Number

